Characterization of SINE-derived piRNAs. Base composition of SINE-derived piRNAs. The X-axis represents the nucleotide position relative to the 5â˛ ends of the piRNAs. The Y-axis represents the percentage of base bias. Lower pane: ping-pong pair analysis. The length of overlap is shown on the horizontal axes. Indicated above each axis is the number of possible overlapping pairs of small RNAs within a specified overlap size. Indicated below each axis is the relative frequency of the 5â˛ base identity for overlapping sequences. The colour code for bases is indicated in the centre box. (TIF 730 kb)